1. Field of the Invention
The subject matter of the invention relates to vehicle stabilization systems and, more particularly, to hydraulic leveling cylinders for such systems.
2. Description of the Background of the Invention
Numerous vehicle stabilization systems have been available in the marketplace. Some vehicle stabilization systems incorporate hydraulic cylinders each of which has the capability of stabilizing and supporting its proportionate share of the weight of the vehicle. Such cylinders are typically capable of supporting from 3,000 to 23,000 pounds each with a corresponding hydraulic fluid line connecting it to a fluid pump. The cylinders may be connected to the pump in series so that up and/or down movement of the cylinder pistons may be synchronized.
Hydraulic leveling cylinders have been provided for vehicle stabilizing systems. All such hydraulic cylinder units, however, have been made of steel adding significantly to the overall weight of the vehicle. For example, a specific hydraulic cylinder unit for a Class A motor home can weigh up to about sixty-five (65) pounds. This weight is multiplied by four because a typical stabilizing system includes four cylinder units. The weight of a steel leveling cylinder system negatively impacts vehicle performance and fuel economy.
Additionally, manufacture of steel hydraulic cylinders is expensive. The steel units must be machined, their piston rods chrome plated, and their various components such as vehicle mounts, ports for hydraulic lines, and fittings welded to the cylinder. These steps add significantly to the labor and overall cost per cylinder unit. Chrome plating requires tanks, fume scrubbers, safety protocols, and other costly health and environmental considerations.
Another problem is that steel cylinders rust. Protective plating processes, such as zinc, use acids that destroy the cylinder seals. Powder and e-coating processes require high firing temperatures that destroy the fluid seals. Rust, therefore, eventually causes the cylinder to leak fluid and fail.
Most cylinders, by design, require one fluid hose to be attached to the top of the cylinder and one hose attached to the bottom of the cylinder. When mounted to the underside of the vehicle, the bottom of the cylinder is generally located just inches from the road surface. Inasmuch as the height may be somewhat adjustable, the cylinders are located close to the vehicle's tires. Road debris from the tires damages the plastic fluid lines attached to the cylinder. When one of these fluid hoses is breached, loss of holding pressure to the entire system results. The cylinders then drift down toward the road surface, which may be hazardous. It is desirable, therefore to eliminate ports on the lower end of the cylinder.
Another issue deals with bothersome noises brought about by ambient temperature change after leveling the vehicle. As hydraulic oil cools, the pressure inside the cylinder decreases causing the piston(s) to settle slightly. Due to the plating of the steel and the complement of ring seals necessitated by those surfaces, there is no oil coating the inside wall of the cylinder gland. Accordingly, no way exists to silence the creaking and cracking sounds that occur during settling as the piston rod slides against the interior wall of the cylinder gland.
There therefore remains a need for a new and improved hydraulic leveling cylinder for a vehicle stabilization system.